class_docstr: Internal model class for training SGD MF.
code: def __init__(self, umat, imat):
      self.user_features = umat
      self.item_features = imat
      self.feature_count = umat.shape[1]
      assert imat.shape[1] == self.feature_count
      self.user_count = umat.shape[0]
      self.item_count = imat.shape[0]
      self.initial_value = np.nan
  
imports: import logging
  import time
  import pandas
  import numpy
  import numba
  from seedbank import numpy_rng
  from .bias import Bias
  from .mf_common import MFPredictor
  from ..None import util
label_desc: Use image node_id 1 to create a new Model object  with example: obj = Model(umat, imat)